Arrangement for return of exhaust gases in supercharged engines with parallel turbines

Abstract

In a supercharged engine, an EGR (Exhaust Gas Recirculation) turbine (6) is incorporated in the exhaust gas flow in parallel with the turbine (4) of the supercharger. The EGR turbine (6) is driven by a first partial exhaust gas flow (21) and is used for driving an EGR compressor (7) which delivers a second partial gas flow (22) which is to be returned to the inlet manifold (2) of the combustion engine. The first and second partial gas flows (21,22) intended respectively to drive the EGR turbine (6) and be returned to the inlet side via the EGR compressor (7) are both tapped from the exhaust manifold (3,3') upstream with respect to the supercharger turbine (4) as seen in the exhaust gas flow direction. The exhaust gas flows through the EGR turbine (6), and the EGR compressor (7) are controlled by individual control valves (15,17).

I claim: 
     
       1. Arrangement for return of exhaust gases in a supercharged combustion engine, which arrangement comprises: a first supercharger turbine;   an exhaust system with an exhaust manifold which receives exhaust gases from the cylinders of the combustion engine and leads the exhaust gases to the first supercharger turbine, the exhaust manifold comprising a first exhaust manifold and a second exhaust manifold, each of which receives exhaust gases from different cylinders of the combustion engine;   an inlet system for supply of inlet air to the cylinders of the combustion engine, the inlet system having a first supercharger compressor which is driven by the first supercharger turbine to pressurize the inlet air in the inlet system;   an exhaust gas duct which communicates with the first exhaust manifold and which leads a first partial exhaust gas flow to the first supercharger turbine;   an exhaust gas return duct which has a first end which communicates with the second exhaust manifold and a second end which communicates with the inlet system;   a second supercharger turbine arranged in parallel with the first supercharger turbine and situated in the exhaust gas duct, the second supercharger turbine being driven by the first partial exhaust gas flow; and   a second supercharger compressor arranged in the exhaust gas return duct and driven by the second supercharger turbine to deliver a second partial exhaust gas flow from the second exhaust manifold to the inlet system at a pressure increased by the second supercharger compressor.   
     
     
       2. Arrangement according to claim 1, wherein the first supercharger turbine is provided with a divided inlet run having one branch arranged to receive exhaust gases from the first exhaust manifold and a second branch arranged to receive exhaust gases from the second exhaust manifold. 
     
     
       3. Arrangement according to claim 1, wherein a first control valve is arranged in the exhaust gas duct and controls the first partial exhaust gas flow therethrough. 
     
     
       4. Arrangement according to claim 3, wherein the first supercharger turbine is of variable geometry. 
     
     
       5. Arrangement according to claim 4, wherein the exhaust gas return duct has its second end connected to the inlet air manifold of the combustion engine downstream, with respect to the direction of flow of the inlet air, of the first supercharger compressor. 
     
     
       6. Arrangement according to claim 5, wherein a gas cooler is provided in the inlet system downstream, with respect to the direction of inlet gas flow, of the first supercharger compressor. 
     
     
       7. Arrangement according to claim 3, wherein a second control valve is arranged in the exhaust gas return duct to control the second partial exhaust gas flow. 
     
     
       8. Arrangement according to claim 7, wherein respective control devices are provided for controlling the first and second control valves. 
     
     
       9. Arrangement according to claim 8, wherein a control device is provided for controlling the geometry of the first supercharger turbine. 
     
     
       10. Arrangement according to claim 8, wherein a control unit is provided to control via the respective control devices the first and second control valves on the basis of respective engine criteria. 
     
     
       11. Arrangement according to claim 9, wherein a control unit is provided to control via the respective control devices the first control valve, the second control valve and the geometry of the first supercharger turbine. 
     
     
       12. Arrangement according to claim 10, wherein sensors arranged on the combustion engine are provided to supply the control unit with signals representing the respective engine parameters. 
     
     
       13. Arrangement according to claim 11, wherein sensors arranged on the combustion engine are provided to supply the control unit with signals representing the respective engine parameters. 
     
     
       14. Arrangement according to claim 12, wherein the control unit is a microcomputer, the respective control devices are controlled electrically and the sensors provide the control unit with electrical input signals. 
     
     
       15. Arrangement according to claim 13, wherein the control unit is a microcomputer, the respective control devices are controlled electrically and the sensors provide the control unit with electrical input signals. 
     
     
       16. Arrangement according to claim 1, wherein means are arranged in the exhaust gas return duct for conditioning the second partial exhaust gas flow which is to be returned to the inlet air manifold of the combustion engine. 
     
     
       17. Arrangement according to claim 16, wherein the conditioning means include a catalyst. 
     
     
       18. Arrangement according to claim 16, wherein the conditioning means include an exhaust gas cooler.